(1) Field of the Invention
This invention relates to an electrostatic flocking product and more particularly to an electrostatic flocking product in which flocks are fixed to the surface to be flocked of a base material through an adhesive layer formed by polyurethane prepared by curing a mixture of an isocyanate prepolymer and polyisocyanate, with water.
(2) Description of the Prior Art
Since an electrostatic flocking product can easily impart soft and graceful visual and tactile feelings to the surface thereof regardless of the kind of the base material used, these products are widely used as textile goods such as clothes, footwares, bags, interior decorations, etc, as well as for electric products such as home warmers, etc., and motorcar parts such as garnishes, trims, weather-strips, glass runs, etc.
As a polymer forming adhesive layers for these electrostatic flocking products, a polyacrylic acid ester, a synthetic rubber (e.g., polychloroprene), polyvinyl acetate, etc., are usually used. However, these polymers are insufficient in abrasion resistance of the flocked surface, in particular, in abrasion resistance thereof under severe using conditions. Accordingly, electrostatic flocking products in which the adhesive layers are formed by water-cured polyurethane having excellent abrasion resistance have now been marketed. The water-cured polyurethane contains in the polyol raw material (mainly composed of high molecular polyols) a small amount of low molecular polyols (e.g., ethylene glycol, porpylene glycol, etc.,) for increasing the heat resistance thereof. The low molecular polyol densifies the distribution of the urethane bond and the aromatic nuclei in the isocyanate prepolymer chain, whereby it contributes to the improvement of the abrasion resistance, heat ressitance, etc., of the flocked surfaces of the electrostatic flocking products, but the presence of the low-molecular polyol increases the intermolecular force of isocyanate prepolymers and decreases the fluidity of the adhesive, which give bad influences on the coating operation for the adhesive layer. In order to improve the fluidity of the adhesive coating composition to a coatable extent, it is necessary to add a large amount of a chlorine series solvent which added at reaction or to use an ignitable polar solvent together with the chlorine series solvent. In the former case, however, the concentration of solid components in the adhesive is lowered, whereby a desired layer thickness (usually 80 to 120 .mu.m) of the adhesive layer is reluctant to obtain by one coating and in the latter case, the coating environment must be cared, which give also bad influences on the coating operation. Furthermore, since the upper limit of the mixing amount of the low molecular polyol to a high molecular polyol is about 0.1 mole (if the amount is over this limit, the adhesive is gelled to make coating impossible), there is a limit on the improvement for the abrasion resistance (particularly, after heat aging) of the flocked surface.